OM-2228 / Operation and Maintenance Manual
120CU20 / Series 500120 / 400 Hz. Generator Set
October 15, 2013
Chapter 2-4
Page 19
Trouble, Symptom, Condition.
Probable Cause.
Test, Check, and/or Remedy.
T-R Controls and Components.
1.
Input AC and Output DC
contactor will not close when “
DC
OUTPUT
” push-button S431 is
pressed. Engine running normally,
AC voltage normal, no load
applied to output cable.
a.
Defective push-button switch
At rated speed, measure the
voltage across the switch. The
voltage should read approximately
5 VDC. Press the switch again
and the voltage should go to 0 V.
If voltage does not go to 0 V, the
switch is defective and needs to
be replaced.
b.
Defective load contactor
Fault Codes Display
•
“
70.46
” for input contactor
•
“
70.31
” for output contactor
Check all wire connections or
replace with a known good
contactor.
If the above works correctly, see
Step “c”.
c.
Defective TRB PC Board
Replace TRB PC board with a
board known to be operating
properly. If contactor still doesn’t
close, contact the factory for
further information.
2.
Load contactor K402 opens
during power delivery. The engine
is still running at rated speed or
has returned to idle.
a.
Defective load contactor.
Fault Codes Display
•
“
70.46
” for input contactor
•
“
70.31
” for output contactor
Check all wire connections or
replace with a known good
contactor.
If the above works correctly, see
Step “c”.
b.
Contactor opening could have
been normal because of an
over/under-voltage condition.
Fault Codes Display
•
“
70.28
” for over-voltage
•
“
70.29
” for under-voltage
Resume operation and closely
observe voltmeter and fault code
gauge for evidence of over/under-
voltage condition. If contactor
opens and no over/under-voltage
condition exists, proceed to Step
c.
c.
Contactor opening could have
been normal because of an
overload or over temperature
condition.
Fault Codes Display
•
“
70.30
” for overload
•
“
70.44 or 70.45
” for over
temperature
Resume operation and closely
observe fault code gauge for
evidence of and overload or over
temperature condition. If contactor
opens and neither condition
applies, proceed to Step d.
d.
Defective TRB PC Board.
Replace TRB PC board with a
board known to be operating
properly. Resume power delivery.
If contactor still opens, contact the
factory for further information.
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